ES2846301T3 - Low energy curing offset printing and letterpress printing inks and printing process - Google Patents

Abstract

A radically curable low energy offset printing or letterpress ink having a viscosity in the range of 2.5 up to 25 Pa s at 40 ° C and 1000 s-1 for printing a security feature on a substrate or printing document. security, radically curable low energy offset printing or letterpress printing ink, comprising: i) from 10% by weight to 80% by weight of radically curable (meth) acrylate compounds; ii) from 1% by weight to 20% by weight of one or more photoinitiators of formula (I): ** (See formula) ** where R1, R2 are identical or different from each other and are selected from the group consisting of hydrogen, C1-C4 alkyls and Si (R15) 3; preferably selected from the group consisting of hydrogen and C1-C4 alkyls, and more preferably hydrogen; R3, R4, R5, R6 are identical to or different from each other and are selected from the group consisting of hydrogen and C1-C4 alkyls, preferably C1-C4 alkyls, and more preferably methyl; R7, R8, R9, R10, R11, R12, R13, R14 are identical or different from each other and are selected from the group consisting of hydrogen, C1-C4 alkyls and halogens, preferably from the group consisting of hydrogen and C1- alkyls. C4, and more preferably hydrogen; and R15 is selected from the group consisting of C1-C4 alkyls, phenyl, C1-C4 hydroxyalkyls and C5-C8 cycloalkyls; iii) from 1% by weight to 60% by weight of one or more machine readable materials selected from the group consisting of luminescent materials, magnetic materials, IR absorbing materials and mixtures thereof; and iv) from 0.5% by weight to 20% by weight of one or more fillers and / or diluents, the weight percentages are based on the total weight of the radically curable low energy offset printing ink. typographic.

Description

DESCRIPTION

Low energy curing offset printing and letterpress printing inks and printing process

Technical field

The present invention relates to the field of security document protection against forgery and illegal reproduction. The present invention relates to the field of radically curable low energy offset printing and letterpress printing inks and processes for producing security features in security documents.

Background of the invention

With the constant improvement in the quality of photocopies and hot prints and in an attempt to protect security documents such as banknotes, valuable documents or cards, tickets or transport cards, tax stamps, and product labels that have no effects reproducible against forgery, falsification or illegal reproduction, it has been the conventional practice to incorporate various means of security in these documents. Typical examples of security media include security threads, windows, fibers, plates, sheets, decals, holograms, watermarks, security inks comprising optically variable pigments, magnetizable or magnetic thin film interference pigments, coated particles of interference, thermochromic pigments, photochromic pigments, luminescent compounds, infrared absorbers, ultraviolet absorbers or magnetic.

Machine-readable inks, such as for example magnetic inks, luminescent inks and IR absorbing inks, have been widely used in the field of security documents, in particular for banknote printing, to confer a security feature on the security document. additional covert. Protecting security documents against counterfeiting and illegal reproduction by providing covert security features is based on the concept that such features typically require specialized equipment and knowledge to detect them. In the field of security and protection of valuable documents and commercial property value against forgery, counterfeiting and illegal reproduction, it is known in the art to apply machine-readable security inks by different printing processes including printing processes using highly colored inks. viscous or pasty such as offset printing, letterpress printing, and relief printing (also known in the art as etched steel stamping or copper plate printing). Radically pigmented UV-curable offset printing inks and radically pigmented UV-curable letterpress printing inks are used in the field of security document protection against counterfeiting and illegal reproduction to be applied as thin layers in security documents in the form of security features.

If the ink doesn't dry quickly and efficiently, the results kick in. Activation occurs when a printing ink that is not dry or cured adheres to the back of a printed substrate placed on top of it during stacking of printed substrates as it exits the presses (see for example US 4,604. 952). This is a particular problem during the printing of security features on security documents, especially banknotes, because such documents typically carry a multitude of overlapping or partially overlapping security features which are applied one after the other. If the previously applied security feature, for example a background image or graphic pattern, has not dried sufficiently yet, the entire multi-pass printing process is not only delayed but the security feature thus obtained may still suffer peeling or marked because it is launched in the machine during any subsequent printing or processing operations.

Conventional banknote printing processes use printing technologies including offset printing, embossing, screen printing, flexographic printing and letterpress printing, in a series of separate stages by drying periods of the newly printed ink layer.

During a conventional banknote printing process, offset inks are applied during one of the first stages of the multi-stage global printing process, where offset printing is followed by an embossing stage. If a security feature is printed on a security document such as a banknote by an offset printing process and if such a security feature suffers from poor surface curing properties, the subsequent embossing step could be delayed or start up. During an embossing printing process (also known in the art as etched copper plate printing and etched steel punch printing), an etched steel cylinder carrying a heated plate etched with a pattern or image to be printed is supplied With inks from inking cylinder (s) (or shablon cylinder), each ink cylinder being inked in at least one corresponding color to form security features. The inked relief plate is brought into contact with the substrate and the ink is transferred under pressure from the embossing of the relief printing plate onto the substrate to be printed forming a thick printing layer in the form of reliefs, said result of thickness of the ink layer and the embossing of the substrate. One of the distinguishing characteristics of the relief printing process is that the thickness of the ink transferred to the Substrate can be varied from a few microns to several tens of microns by using correspondingly deep or respectively deep recesses of the relief printing plate. Consequently, it is critical that offset inks are completely dry before embossing begins in order to avoid any output problems, such starting items become pronounced in the subsequent embossing process due to the high pressure applied. to stacks of printed substrates.

During a conventional banknote printing process, letterpress inks are applied during one of the last stages of the multi-stage global printing process, where letterpress printing is followed by a cutting process using for example a cutter or guillotine where the sheets comprising a plurality of bills are cut to form individual bills for circulation. If a security feature is printed on a security document such as a banknote by a letterpress printing process and if such a security feature suffers from poor surface curing properties, the next cutting step could be delayed or a failure may occur. start up. Letterpress printing (also known in the art as letterpress and letterpress printing), is a method that consists of transferring an ink from a hard metal printing plate that comprises embossed elements, such as letters, numbers, symbols, lines or points. The raised printing elements are coated with a layer of ink of constant thickness by the application of rollers. The ink is then transferred to an article or a substrate. The letterpress printing technique is typically used for the purpose of numbering the banknotes, that is to provide banknotes with one or more unique serial numbers. Consequently, it is critical that the letterpress inks are completely dry before starting the cutting stage in order to avoid any of the output problems, said starting elements are pronounced in the next cutting stage process due to the high pressure applied. to stacks of printed substrates.

Radically UV curable inks cure by free radical mechanisms consisting of the energy activation of one or more free radical photoinitiators that release free radicals which in turn initiate polymerization to form a layer or coating. Known free radical photoinitiators include acetophenones, benzophenones, alpha-aminoketones, alpha-hydroxyketones, phosphine oxides and derivatives of phosphine oxide and benzyldimethyl ketals.

With the aim of providing environmentally friendly solutions, UV Mercury Medium Pressure Lamps and Systems have been developed to cure inks with low energy (LE or HUV). Low energy mercury medium pressure lamps have emission spectrum in UV-A and UV-B regions and have less than 5% of UV energy in UV-C emission. Such systems and lamps produce a reduced amount of emitted light at the ozone generating wavelengths of the spectrum that is produced with conventional UV lamps such as medium pressure mercury lamps.

The UV curing efficiency of an ink coating or layer depends not only on the overlap of the emission spectrum of the irradiation source used for such curing and the absorption spectrum of the photoinitiator comprised in the ink coating or layer but also on the intensity of the emission spectrum of the irradiation source and in the molar absorption coefficient of the photoinitiator at the wavelength of the emission spectrum of the irradiation source. Consequently, UV curing of ink coatings or layers comprising free radical photoinitiators conventionally used with UV-LE lamps experience reduced curing efficiency as a result of poor overlap of UV-LE lamp emission spectrum with absorption of such conventionally used free radical photoinitiators, leading to slow or poor cure or cure defects.

Since machine-readable security inks typically comprise a high amount of pigments, such inks are particularly difficult to cure due to the filtering effect of such pigments that reduce the amount of UV radiation available to photoinitiators.

In order to overcome the poor curing properties of UV curing with UV-LE lamps, acyl-phosphine photoinitiators have been used due to their redshift absorption spectrum. However, acyl phosphine photoinitiators are known to be particularly sensitive to oxygen inhibition and not highly efficient for surface curing or thin layer curing. Oxygen inhibition during UV curing of coating layers is particularly a problem for thin UV-curable layers.

Therefore, there remains a need for low energy curable offset pigment and letterpress printing inks, and processes for printing security features on high speed (this is industrial speed) security documents, such print security features that combine good surface cure and good cure properties after such inks have been cured with a radiation wavelength of 280 to 400 nm (low energy lamps).

Summary of the invention

Accordingly, it is an objective of the present invention to overcome the shortcomings of the prior art as discussed above. This is achieved by the provision of a use of one or more photoinitiators of formula (I) in a radically curable offset printing or letterpress ink, wherein such offset printing ink radically curable or letterpress printing has a viscosity in the range of about 2.5 to about 25 Pa s at 40 ° C and 1000 s-1 and comprises radically curable (meth) acrylate compounds, one or more machine-readable materials selected from the group consisting of luminescent materials, magnetic materials, IR absorbing materials and mixtures thereof, and one or more fillers and / or diluents.

The subject matter of the present invention is defined in claims 1-10 as attached. The embodiments described herein that are not covered by the claims serve merely to illustrate the technical context of the present invention.

There are described herein low energy radically curable offset printing or letterpress printing inks having a viscosity in the range of about 2.5 to about 25 Pa s at 40 ° C and 1000 s-1 to print a characteristic of security on a security substrate or document, such low energy radically curable offset printing or letterpress ink comprises:

i) from about 10% by weight to about 80% by weight of radically curable (meth) acrylate compounds;

ii) from about 1% by weight to about 20% by weight of one or more photoinitiators of formula (I):

where

R ¹ , R ² are identical or different from each other and are selected from the group consisting of hydrogen, C1-C4 alkyls and Si (R ¹⁵ ) ³ ; preferably selected from the group consisting of hydrogen and C1-C4 alkyls, and more preferably hydrogen;

R ³ , R ⁴ , R ⁵ , R ⁶ are identical to or different from each other and are selected from the group consisting of hydrogen and C1-C4 alkyls, preferably C1-C4 alkyls, and more preferably methyl;

R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ are identical or different from each other and are selected from the group consisting of hydrogen and C1-C4 alkyls and halogens, preferably from the group consisting of hydrogen and C1-C4 alkyls, and more preferably hydrogen; Y

R ¹⁵ is selected from the group consisting of C1-C4 alkyls, phenyl, C1-C4 hydroxyalkyls and C5-C8 cycloalkyls; iii) from about 1% by weight to about 60% by weight of one or more machine-readable materials selected from the group consisting of luminescent materials, magnetic materials, IR absorbing materials, and mixtures thereof; Y

iv) from about 0.5% by weight to about 20% by weight of one or more fillers and / or diluents, the weight percentages are based on the total weight of the radically curable low energy offset printing ink or letterpress printing.

Described herein are processes for producing for printing a security feature on a substrate by an offset or letterpress printing process comprising the steps of applying the low energy radically curable offset printing ink or letterpress printing described herein by offset printing or letterpress printing to form a coating or layer, and curing the coating or layer with a UV lamp (280 to 400 nm) at a dose of at least 50 mJ / cm ² , preferably at least 100 mJ / cm ²

Also disclosed herein are security features comprising a layer or coating made from the radically curable low energy offset printing or letterpress ink described herein. Described herein are uses of the security features described herein for the protection of a security document against forgery or fraud and security documents comprising one or more of the security features described herein.

Also described herein are security documents that comprise one or more security features described herein.

Also described herein are uses of one or more photoinitiators described herein in an amount of from about 1% by weight to about 20% by weight to produce a radically curable low energy offset printing or letterpress ink that have a viscosity in the range of about 2.5 to about 25 Pa s at 40 ° C and 1000 s-1, such a radically curable low energy offset printing ink or letterpress printing ink being suitable for printing a security feature on a security document, such ink Radically curable low energy offset printing or letterpress printing comprises

i) from about 10% by weight to about 80% by weight of radically curable (meth) acrylate compounds;

ii) from about 1% by weight to about 60% by weight of one or more machine-readable materials selected from the group consisting of luminescent materials, magnetic materials, IR absorbing materials, and mixtures thereof; Y

iii) from about 0.5% by weight to about 20% by weight of one or more fillers and / or diluents, the weight percentages are based on the total weight of the radically curable low energy offset printing ink or letterpress printing.

Detailed description

Definitions

The following definitions clarify the meaning of the terms used in the description and in the claims. As used herein, the indefinite article "a" indicates one as well as more than one and does not necessarily limit its noun referring to the singular.

As used herein, the term "around" means that the quantity, value or limit in question may be the specific designated value or some other value in its vicinity. Generally, the term "around" denotes that a certain value is intended to denote a range within ± 5% of the value. For example, the phrase "around 100" denotes a range of 100 ± 5, that is, the range from 95 to 105. Generally, when the term "around" is used, similar effects or results can be expected according to the invention can be obtained within a range of ± 5% of the indicated value. However, a specific amount, value or limit supplemented with the term "about" is intended herein to also describe the same amount, value or limit as such, that is without the supplement "about".

As used herein, the term "and / or" means that either all or only one of the elements of such a group may be present. For example, "A and / or B" will mean "only A, or only B, or both A and B". In the case of “only A”, the term also covers the possibility that B is absent, this is “only A, but not B”.

As used herein, the term "one or more" means one, two, three, four, and so on.

The term "comprising" as used herein is intended to be non-exclusive or overt. Thus, for example an ink comprising a compound A may include other compounds in addition to A. However, the term "comprising" also covers, as a particular embodiment thereof, the more restrictive meanings of "consisting essentially of" and "Consisting of", so that for example "an ink comprising compound A" may also (essentially) consist of compound A.

Where the present description refers to "preferred" embodiments / features, combinations of these "preferred" embodiments / features will also be considered described as long as this combination of "preferred" embodiments / features is technically significant.

The term "security feature" is used to denote an image, pattern, or graphic element that can be used for authentication purposes.

The term "security document" refers to a document that is normally protected against forgery or fraud by at least one security feature. Examples of security documents include without limitation documents of value and value of commercial property.

Descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or limit the present invention to the precise forms described, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to better explain the principles of the present invention and its practical application, thus allowing others skilled in the art to make the best use of the present invention and various embodiments with various modifications as are suitable for the private use contemplated.

The present invention provides radically curable low energy offset printing or letterpress inks for producing (printing) a security feature on a security document by an offset printing process or by a letterpress printing process. The present invention further provides security features comprising a coating or a layer made of the radically curable low energy offset printing or letterpress ink described herein and security documents comprising one or more security features described herein.

The low energy radically curable offset printing or letterpress ink described herein has a viscosity in the range of about 2.5 to about 25 Pa s at 40 ° C and 1000 s -1; Viscosities are measured on a Haake Roto-Visco RV1 with a 2 cm 0.5 ° cone.

The low energy radically curable offset printing or letterpress ink described herein comprises radically curable (meth) acrylate compounds. The radically curable (meth) acrylate compounds described herein are present in an amount of from about 10% by weight to about 80% by weight, preferably from about 20% by weight to about 80% by weight, Weight percentages are based on the total weight of the low energy radically curable offset printing or letterpress ink described herein.

Radically curable compounds are cured by free radical mechanisms consisting of the energy activation of one or more photoinitiators that release free radicals which in turn initiate polymerization to form a layer or coating.

The preferably disclosed radically curable (meth) acrylate compounds consist of one or more radically curable (meth) acrylate oligomers and one or more radically curable (meth) acrylate monomers. The term "(meth) acrylate" in the context of the present invention refers to acrylate as well as the corresponding methacrylate. Radically curable (meth) acrylate oligomers are described herein preferably selected from the group consisting of polyepoxy (meth) acrylates, (meth) acrylated oils, (meth) acrylated epoxidized oils, polyester (meth) acrylates, (meth) ) polyether acrylates, aliphatic or aromatic polyurethane (meth) acrylates, silicone (meth) acrylates, polyamino (meth) acrylates, polyacrylic acid (meth) acrylates, polyacrylate ester (meth) acrylates and mixtures thereof , more preferably selected from the group consisting of polyepoxy (meth) acrylates, (meth) polyester acrylates, aliphatic or aromatic (meth) polyurethane acrylates, silicone (meth) acrylates, polyamino (meth) acrylates, (meth) polyacrylic acid acrylates, polyacrylate ester (meth) acrylates, and mixtures thereof. Radically curable (meth) acrylate monomers are described herein preferably selected from the group consisting of 2 (2-ethoxyethoxy) ethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, C12 alkyl (meth) acrylate / C14, C16 / C18 alkyl (meth) acrylate, caprolactone (meth) acrylate, cyclic trimethylolpropane formal (meth) acrylate, nonylphenol (meth) acrylate, isobornyl (meth) acrylate, isodecyl (meth) acrylate, ( lauryl meth) acrylate, stearyl (meth) acrylate, octyldecyl (meth) acrylate, tridecyl (meth) acrylate, methoxy poly (ethylene glycol) (meth) acrylate, polypropylene glycol (meth) acrylate, (meth) acrylate tetrahydrofu rfu rile, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 3-methyl-1,5-pentanedioldi ( meth) acrylate, alkoxylated di (meth) acrylate, esterdiol di (meth) acrylate, bisphenol A di (meth) acrylate, bisphenol A ethoxylate di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, ethylene glycol di ( I t) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate , neopentyl glycol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, trimethylolpropane tri (me) acrylate, glyceryl tri (meth) acrylate, propoxylated trimethylolpropane tri (me) acrylate, propoxylated tri (meth) acrylate glyceryl, propoxylated tri (meth) acrylate pentaerythritol (meth) acrylate, pentaerythritol tetra (meth) acrylate, propoxylated pentaerythritol tri (me) acrylate, trimethylolpropane tri (meth) acrylate, tris (2-hydroxy ethyl) isocyanurate tri (meth) acrylate, tetra (meth) ditrimethylolpropane acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate (methyl acrylate) dipentaerythritol and its ethoxylated equivalents as well as mixtures of mi smos, more preferably from the group consisting of 2-phenoxyethyl (meth) acrylate, isodecyl (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, tri (meth) trimethylolpropane acrylate, pentaerythritol tri (meth) acrylate and their ethoxylated equivalents as well as mixtures thereof, and still more preferably from the group consisting of trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PTA), tripropylene glycol D diacrylate (DPGDA), 1,6-hexanediol diacrylate (HDDA) as well as mixtures thereof.

The low energy radically curable offset printing or letterpress ink described herein comprising the (meth) acrylate compounds described herein may further comprise one or more vinyl ethers and / or their ethoxylated equivalents. Suitable vinyl ethers may be selected from the group consisting of ethyl vinyl ether (EVE), n-butyl vinyl ether (NBVE), iso-butyl vinyl ether (IBVE), cyclohexyl vinyl ether (CHVE), 2-ethylhexyl vinyl ether. (EHVE), 1,4-butanediol divinyl ether (BDDVE), diethylene glycol divinyl ether (DVE-2), triethylene glycol divinyl ether (DVE-3), 1,4-cyclohexanedimethanol divinyl ether (CHDM-di), hydroxybutyl vinyl ether ( HBVE), 1,4-cyclohexanedimethanol mono vinyl ether (CHDM-mono).

The low energy radically curable offset printing or letterpress ink described herein comprises one or more photoinitiators of formula (I):

where

R ¹ , R ² are identical or different from each other and are selected from the group consisting of hydrogen, C1-C4 alkyls (e.g. methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec-butyl, tert-butyl , cyclobutyl) and Si (R ¹⁵ ) a;

R ³ , R ⁴ , R ⁵ , R ⁶ are identical or different from each other and are selected from the group consisting of hydrogen and C1-C4 alkyls (e.g. methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec -butyl, tert-butyl, cyclobutyl);

R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ are identical or different from each other and are selected from the group consisting of hydrogen, C1-C4 alkyls (e.g. methyl, ethyl , propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl) and halogens, in particular fluorine, chlorine and bromine; Y

R ¹⁵ is selected from the group consisting of C1-C4 alkyls, phenyl, C1-C4 hydroxyalkyls and C5-C8 cycloalkyls. According to a preferred embodiment, the low energy radically curable offset printing or letterpress ink described herein comprises one or more photoinitiators of formula (I) wherein R ¹ , R ² are identical or different from each other. and are selected from the group consisting of hydrogen and C1-C4 alkyls (eg methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl), and more preferably hydrogen;

R ³ , R ⁴ , R ⁵ , R ⁶ are identical or different from each other are C1-C4 alkyls (e.g. methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl) , preferably C1 alkyls (this is methyl); and R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ are identical or different from each other and are selected from the group consisting of hydrogen, C1-C4 alkyls (e.g. methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl) and halogens, in particular fluorine, chlorine and bromine, preferably from the group consisting of hydrogen and C1-C4 alkyls, and more preferably hydrogen.

According to a more preferred embodiment, the low energy radically curable offset printing or letterpress ink described herein comprises one or more photoinitiators, wherein at least one of such one or more photoinitiators is of formula (II) :

It should be further appreciated that the invention also extends to compounds in which one or more of the atoms have been replaced by an isotopic variant, such as for example one or more hydrogen atoms can be replaced by 2H or 3H and / or one or more carbon atoms can be replaced by 14C or 13C.

Compounds of structure (II) suitable as photoinitiators are described herein commercially available as ESACURE® KIP 160 from IGM, The Netherlands, (CAS number 71868-15-0).

One or more photoinitiators comprised in the radically curable low energy offset printing or letterpress ink are described herein preferably present in a total amount of from about 1% by weight to about 20% by weight, more preferably about 1% by weight to about 15% by weight, the weight percentages are based on the total weight of the radically curable low energy offset printing or letterpress ink described herein.

The low energy radically curable offset printing or letterpress ink described herein may further comprise one or more inert resins (that is, resins that do not participate in the reaction of polymerization). Inert resins can be used to adjust the viscosity of the radically curable offset printing or letterpress ink described herein to lower the glass transmission temperature of an ink layer prepared with the radically curable or letterpress offset printing ink. letterpress printing described herein, or to increase the adhesion of an ink layer prepared with the radically curable offset printing ink or letterpress printing described herein. The one or more inert resins are preferably selected from the group consisting of hydrocarbons (such as for example styrene-based hydrocarbon resins), acrylics (such as for example acrylic copolymers), styrene allyl alcohols, phenolic resins, rosin modified resins, ketone resins, alkyd resins, and mixtures thereof. When presented, one or more inert resins described herein are presented in the offset or letterpress wet-curable low energy printing ink described herein in an amount of from about 0.1% by weight to about 10% by weight. weight, preferably in an amount of from about 0.5% by weight to about 2% by weight, the weight percentages are based on the total weight of the letterpress or offset wet curable low energy printing ink described herein. .

The low energy radically curable offset printing or letterpress ink described herein may further comprise one or more sensitizers in conjunction with one or more photoinitiators in order to achieve efficient cure. Typical examples of suitable sensitizers include without limitation isopropylthioxanthone (ITX), 1-chloro-2-propoxy-thioxanthone (CPTX), 2-chloro-thioxanthone (CTX), 2-methoxythioxanthone (MeOTX), and 2,4-diethyl-thioxanthone ( DETX), polymeric derivatives thereof, and mixtures thereof. When presented, one or more sensitizers described herein are presented in the radically curable low energy offset printing or letterpress ink in an amount of from about 0.1% by weight to about 5% by weight, preferably In an amount of from about 0.5% by weight to about 2% by weight, the weight percentages are based on the total weight of the radically curable low energy offset printing or letterpress printing ink described herein.

The low energy radically curable offset printing or letterpress ink described herein may further comprise one or more UV stabilizers in order to stabilize such particular ink during storage. Typical examples of suitable UV stabilizers include without limitation, hydroquinone, hydroquinone monomethyl ether, 4-t-butylcatechol, 4-t-butyl-phenol, 2,6-di-t-butyl-4-methyl-phenol (BHT), pyrogallol , phenothiazine (PTZ), 2,4-diazabicyclo [2.2.2] octane (DABCO), copper (II) salts (such as for example copper (II) phenoxide, copper (II) acetylacetonate, copper gluconate ( II), copper (II) tartrate, copper (II) acetate, copper (II) carbamate, copper (II) thiocarbamate, copper (II) dithiocarbamate or copper (II) dimethyl dithiocarbamate), copper salts ( I) (such as for example copper (I) chloride or copper (I) acetate), tris [N- (hydroxyl-KO) -N- (nitroso-KO) benzenaminate] -aluminum and mixtures thereof. When present, one or more UV stabilizers described herein are present in the radically curable low energy offset printing or letterpress ink in an amount of from about 0.1% by weight to about 5% by weight, preferably in an amount of from about 0.5% by weight to about 2% by weight, the weight percentages are based on the total weight of the radically curable low energy offset printing or letterpress ink described herein. .

The radically curable low energy offset printing or letterpress ink described herein further comprises one or more machine-readable materials selected from the group consisting of luminescent materials, magnetic materials, IR absorbing materials, and mixtures thereof. As used herein, the term "machine-readable material" refers to a material that exhibits at least one distinctive property that is detectable by a device or machine, such as for example a magnetic detector (when the readable materials in machine have magnetic properties) or an IR chamber (when machine readable materials have IR absorbing properties), and which may be comprised of a safety feature made from radically curable low energy offset printing ink or printing typographic described herein in order to confer a way to authenticate such security feature by the use of a particular equipment for its detection and / or authentication. One or more machine-readable materials described herein are presented in an amount of from about 1% by weight to about 60% by weight, preferably from about 5% by weight to about 40% by weight, the percentages in Weights are based on the total weight of the radically curable low energy offset printing or letterpress ink.

Typical example of luminescent materials includes without limitation inorganic pigments (inorganic housing crystals or glasses altered with luminescent ions), organic or organometallic substances (complexes of luminescent ion (s) with organic ligand (s)). Luminescent compounds can absorb certain types of energy acting on them and subsequently emit at least partially this absorbed energy as electromagnetic radiation. Luminescent compounds are detected by exposing them to a certain wavelength of light and analyzing the emitted light. Down-converting luminescent compounds absorb electromagnetic radiation at a higher frequency (shorter wavelength) and at least partially re-emit it at a lower frequency (longer wavelength). Up-converting luminescent compounds absorb electromagnetic radiation at a lower frequency and at least partially re-emit part of it at a higher frequency. The emission of light from luminescent materials arises from excited states in atoms or molecules. Radiation decay of such excited states has a characteristic decay time, which is material dependent and can range from 10.9 seconds to several hours. Both compounds fluorescent and phosphorescent are suitable for the present invention. In the case of phosphorescent compounds, the measurement of deterioration characteristics can also be carried out and used as a machine-readable characteristic. Luminescent compounds in pigment form have been widely used in inks (see US 6565770, WO 2008/033059 A2 and WO 2008/092522 A1). Examples of luminescent compounds include but are not limited to sulfides, oxysulfides, phosphates, vanadates, etc. non-luminescent cations, altered with at least one luminescent cation selected from the group consisting of transition metals and the rare earth ions; Rare earth oxysulfides and rare earth metal complexes such as those described in WO 2009/005733 A2 or in US 7 108 742. Examples of inorganic composite materials include without limitation La2O2S: Eu, ZnSiO4: Mn, and YVO4: Nd. When presented, one or more luminescent materials are preferably presented in an amount of from about 1 to about 30% by weight, the weight percentages are based on the total weight of the low energy or radically curable offset printing ink. letterpress printing.

Magnetic materials exhibit detectable magnetic properties, particular of the ferromagnetic or ferrimagnetic type and include permanent magnetic materials (hard magnetic materials with Hc coercivity> 1000 A / m) and magnetizable materials (soft magnetic materials with Hc coercivity <= 1000 A / m according to to IEC60404-1 (2000)). Typical examples of magnetic materials include iron, nickel, cobalt, manganese and their magnetic alloys, carbonyl iron, chromium dioxide CrO2, magnetic iron oxides (for example Fe2O3; Fe3O4), magnetic ferrites M (N) Fe (IN) 2O4 and hexaferrites M (N) Fe (IN) 12O ¹⁹ , the magnetic garnets M (NI) 3Fe (NI) 5O12 (such as Yttrium iron garnet Y3FesO12) and their magnetic isostructural substitution products and permanently magnetized particles (for example CoFe2O4) . Magnetic pigment particles comprising a magnetic core material that is surrounded (coated) by at least one layer of another material such as those described in WO 2010/115986 A2 can also be used by the present invention. When presented, one or more magnetic materials are preferably presented in an amount of from about 5 to about 60% by weight, the weight percentages are based on the total weight of the low energy or radically curable offset printing ink. letterpress printing.

Infrared (IR) absorbing materials, that is absorbing materials in the near infrared (NIR) range of the electromagnetic spectrum, more generally in the wavelength range of 700 nm to 2500 nm, are widely known and used as materials. markup in security applications to give printed documents an additional, covert, security element to aid in their authentication. For example, security features that have IR absorbing properties have been implemented in banknotes for use by automatic currency processing equipment, in banking applications and vending machines (ATMs, automatic vending machines, etc.), in order to to recognize a given coin account and to verify its authenticity, in particular to discriminate it from replicas made by color copiers. IR absorbent materials include inorganic IR absorbent materials, eyeglasses comprising substantial amounts of IR absorbent atoms or ions or entities that visualize IR absorption as a cooperative effect, organic IR absorbent materials and organometallic IR absorbent materials (complexes of cation (s) with organic ligand (s), wherein either the separated cation and / or the separated ligand, or both together, have IR absorption properties). Typical examples of IR absorbing materials include among others carbon black, quinone-diimonium or amine salts, polymethines (eg cyanines, squaraines, croconains), phthalocyanine or naphthalocyanine type (IR absorbing pi system), dithiolenes, quaterylene diimides , metal phosphates (eg transition metals or lanthanides), lanthanum hexaboride, indium tin oxide, nanoparticulate antimony tin oxide and altered tin (IV) oxide (cooperative property of SnO4 crystal). IR absorbing materials that comprise a transition element compound and whose infrared absorption is a consequence of electronic transitions within the d shell of transition element atoms or ions such as those described in WO 2007/060133 A2 also can be used by the present invention. When present, one or more IR absorbent materials are preferably presented in an amount of from about 1 to about 40% by weight, the weight percentages are based on the total weight of the low energy radically curable offset printing ink. or letterpress printing.

The low energy radically curable offset printing or letterpress ink described herein further comprises one or more fillers and / or diluents in an amount of from about 0.5 to about 20% by weight, preferably from about 1 up to about 10% by weight, the weight percentages are based on the total weight of the radically curable low energy offset printing or letterpress ink. Preferably one or more fillers and / or diluents are selected from the group consisting of carbon fibers, talcs, micas (muscovites), wollastonites, clay (calcined clay and porcelain clay), kaolins, carbonates (eg calcium carbonate, sodium aluminum carbonate), silicates (eg magnesium silicate, aluminum silicate), sulfates (eg magnesium sulfate, barium sulfate), titanates (eg potassium titanate), alumina hydrates, silica (which also includes fumed silicas ), montmorillonites, graphites, anatases, rutiles, bentonites, vermiculites, zinc whites, zinc sulphides, wood flours, quartz flours, natural fibers, synthetic fibers and combinations thereof. More preferably, one or more fillers and / or diluents are selected from the group consisting of carbonates (eg, calcium carbonate, sodium aluminum carbonate), silicas, talcs, clays, and mixtures thereof.

The radically curable low energy offset printing or letterpress ink described herein it may further comprise a) one or more colorants, and / or b) inorganic pigments, organic pigments or mixtures thereof. Suitable dyes for inks are known in the art and are preferably selected from the group consisting of reactive dyes, direct dyes, anionic dyes, cationic dyes, acid dyes, basic dyes, food dyes, metal complex dyes, solvent dyes, and mixtures. thereof. Typical examples of suitable colorants include without limitation curamines, cyanines, oxazines, uranines, phthalocyanines, indolinocyanines, triphenylmethanes, naphthalocyanines, indonanaphthalo metal dyes, anthraquinones, anthrapyridones, azo dyes, rhodamines, squaryl dyes, croconium dyes. Typical examples of suitable colorants for the present invention include without limitation CI

Acid Yellow 1, 3, 5, 7, 11, 17, 19, 23, 25, 29, 36, 38, 40, 42, 44, 49, 54, 59, 61, 70, 72, 73, 75, 76, 78, 79, 98, 99, 110, 111, 121, 127, 131, 135, 142, 157, 162, 164, 165, 194, 204, 236, 245; C.I. Direct Yellow 1, 8, 11, 12, 24, 26, 27, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 106, 107, 110, 132, 142, 144; C.I. Basic Yellow 13, 28, 65; C.I.

Flash Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42; C.I. Food Yellow 3, 4; C.I. Acid Orange 1, 3, 7, 10, 20, 76, 142, 144; C.I. Basic Orange 1,2,59; C.I. Orange from Food 2; C.I. Orange B; C.I. Acid Red 1, 4, 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 37, 42, 51, 52, 57, 73, 75, 77, 80, 82, 85, 87, 88, 89, 92, 94, 97, 106, 111, 114, 115, 117, 118, 119, 129, 130, 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 180, 183, 184, 186, 194, 198, 209, 211, 215, 219, 221, 249, 252, 254, 262, 265, 274, 282, 289, 303, 317, 320, 321, 322, 357, 359; C.I. Basic Red 1, 2, 14, 28; C.I. Direct Red 1, 2, 4, 9, 11, 13, 17, 20, 23, 24, 28, 31, 33, 37, 39, 44, 46, 62, 63, 75, 79, 80, 81, 83, 84, 89, 95, 99, 113, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230, 231, 253; C.I. Reactive Red 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 15, 16, 17, 19, 20, 21, 22, 23, 24, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 49, 50, 58, 59, 63, 64, 108, 180; C.I. Food Red 1, 7, 9, 14;

C.I. Acid Blue 1, 7, 9, 15, 20, 22, 23, 25, 27, 29, 40, 41, 43, 45, 54, 59, 60, 62, 72, 74, 78, 80, 82, 83, 90, 92, 93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, 131, 138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 171, 182, 183, 184, 187, 192, 193, 199, 203, 204, 205, 229, 234, 236, 249, 254, 285; C.I. Basic Blue 1, 3, 5, 7, 8, 9, 11, 55, 81; C.I. Direct Blue 1, 2, 6, 15, 22, 25, 41, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 120, 123, 158, 160, 163, 165, 168, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248, 249; C.I. Reactive Blue 1, 2, 3, 4, 5, 7, 8, 9, 13, 14, 15, 17, 18, 19, 20, 21,25, 26, 27, 28, 29, 31, 32, 33, 34, 37, 38, 39, 40, 41, 43, 44, 46, 77; C.I. Food Blue 1, 2; C.I. Acid Green 1, 3, 5, 16, 26, 104; C.I. Basic Green 1, 4; C.I: Green Food 3; C.I. Acid Violet 9, 17, 90, 102, 121; C.I. Basic Violet 2, 3, 10, 11, 21; C.I. Acid Chestnut 101, 103, 165, 266, 268, 355, 357, 365, 384; C.I. Basic Chestnut 1; C.I. Acid Black 1, 2, 7, 24, 26, 29, 31, 48, 50, 51, 52, 58, 60, 62, 63, 64, 67, 72, 76, 77, 94, 107, 108, 109, 110, 112, 115, 118, 119, 121, 122, 131, 132, 139, 140, 155, 156, 157, 158, 159, 191, 194; C.I. Direct Black 17, 19, 22, 32, 39, 51, 56, 62, 71, 74, 77, 94, 105, 106, 107, 108, 112, 113, 117, 118, 132, 133, 146, 154, 168; C.I. Reactive Black 1, 3, 4, 5, 6, 8, 9, 10, 12, 13, 14, 18, 31; C.I. Food Black 2; C.I. Solvent Yellow 19, C.I. Solvent Orange 45, C.I. Solvent Red 8, C.I. Solvent Green 7, C.I. Solvent Blue 7, C.I. Solvent Black 7; C.I. Disperse Yellow 3, C.I. Disperse Red 4, 60, C.I. Disperse Blue 3, and metal azo dyes described in US 5,074,914, US 5,997,622, US 6,001,161, JP 02-080470, JP 62-190272, JP 63-218766. Suitable dyes for the present invention can be infrared absorbing dyes or luminescent dyes. When presented, one or more colorants used in the radically curable low energy offset printing or letterpress ink are described herein preferably present in an amount of from about 1 to about 30% by weight, the percentages by weight are based on the total weight of radically curable low energy offset printing or letterpress ink.

Typical examples of organic and inorganic pigments include without limitation C.I. Pigment Yellow 12, C.I.

Pigment Yellow 42, C.I. Pigment Yellow 93, C.I. Pigment Yellow 110, C.I. Pigment Yellow 147, C.I.

Pigment Yellow 173, C.I. Pigment Orange 34, C.I. Pigment Orange 48, C.I. Pigment Orange 49, C.I. Orange Pigment 61, C.I. Pigment Orange 71 C.I. Pigment Orange 73, C.I. Pigment Red 9, C.I.

Pigment Red 22, C.I. Pigment Red 23, C.I. Pigment Red 67, C.I. Pigment Red 15 122, C.I. Pigment Red 144, C.I. Pigment Red 146, C.I. Pigment Red 170, C.I. Pigment Red 177, C.I. Pigment Red 179, C.I. Pigment Red 185, C.I. Pigment Red 202, C.I. Pigment Red 224, C.I. Chestnut Pigment 6, C.I. Chestnut Pigment 7, C.I.

Pigment Red 242, C.I. Pigment Red 254, C.I. Pigment Red 264, C.I. Chestnut Pigment 23, C.I. Pigment Blue 15, C.I. Pigment Blue 15: 3, C.I. Pigment Blue 60, C.I. Pigment Violet 19, C.I. Pigment Violet 23, C.I. Pigment Violet 32, C.I. Pigment Violet 37, C.I. 20 Pigment Green 7, C.I. Pigment Green 36, C.I. Pigment Black 7, C.I.

Pigment Black 11, C.I. Pigment White 4, C.I Pigment White 6, C.I. Pigment White 7, C.I. Pigment White 21, C.I. Pigment White 22, Antimony Yellow, Lead Chromate, Lead Chromate Sulfate, Lead Molybdate, Ultramarine Blue, Cobalt Blue, Manganese Blue, Green Chromium Oxide, Green Hydrated Chromium Oxide, Cobalt Green, Cerium Sulfide, Cadmium Sulfide , cadmium sulfoselenides, zinc ferrite, bismuth vanadate, Prussian blue, mixed metal oxides, azo, azomethine, methine, anthraquinone, phthalocyanine, perinone, perylene, diketopyrrolopyrrole, thioindigo, thiazinindigo, dioxazine, iminoisoindoline, quinoisoindoline, flavantrone, indantrone, anthrapyrimidine and quinophthalone pigments. When presented, the inorganic pigments, organic pigments or mixtures thereof described herein are preferably presented in an amount of from about 0.1 to about 45% by weight, the weight percentages are based on the total weight of the ink. radically curable low energy offset printing or letterpress printing.

The low energy radically curable offset printing or letterpress ink described herein may further comprise one or more waxes preferably selected from the group consisting of synthetic waxes, petroleum waxes and natural waxes. Preferably one or more waxes are selected from the group consisting of amide waxes, erucamide waxes, paraffin waxes, polyethylene waxes, polypropylene waxes, fluorocarbon waxes, polytetrafluoroethylene waxes, Fischer-Tropsch waxes, silicone fluids, beeswax, candelilla waxes, montane waxes, carnauba waxes and mixtures thereof, most preferably selected from the group consisting of paraffin waxes, polyethylene waxes, fluorocarbon waxes, polytetrafluoroethylene waxes, carnauba waxes and mixtures thereof. When presented, the one or more waxes are preferably presented in an amount of from about 0.1 to about 5% by weight, the weight percentages are based on the total weight of the radically curable low energy offset printing ink or letterpress printing.

As is known to those skilled in the art, the low energy radically curable offset printing or letterpress ink described herein may further comprise one or more solvents and / or diluents.

The low energy radically curable offset printing or letterpress ink described herein may further comprise additives including, but not limited to, one or more of the following components as well as combinations thereof: co-initiators, anti - sedimentation, anti-foaming agents, surfactants and other processing aids known in the field of inks. The additives described herein may be present in the low energy curable wet-printing offset inks described herein in amounts and in forms known in the art, including in the form of so-called nanomaterials where at least one of the dimensions of the particles is in the range of 1 to 1000 nm.

The low energy radically curable offset printing or letterpress ink described herein is typically prepared by a method comprising a step of dispersing, mixing and / or grinding all of the ingredients described herein, one or more readable materials. machine described herein, one or more one or more fillers and / or diluents described herein, one or more colorants described herein when presented, inorganic pigments, organic pigments, or mixtures thereof described herein when One or more waxes described herein are presented when presented, and one or more additives when presented in the presence of the (meth) acrylate compounds described herein, thus forming pasty compositions. One or more photoinitiators described herein can be added to the ink either during the stage of dispersing or mixing all the other ingredients or they can be added at a later stage. As described herein, the process described herein comprises a step of applying the radically curable low energy offset printing or letterpress ink described herein by offset printing or letterpress printing to form a coating or layer, and curing the coating or layer with a UV lamp (280 to 400 nm) at a dose of at least 50 mJ / cm2, preferably at least 100 mJ / cm2. As described below, the dose can be measured using a Power Puck® II UV radiometer from EIT, Inc., USA.

The coating or layer made from the radically curable low energy offset printing or letterpress ink described herein is UV cured with a UV LE lamp preferably selected from Baldwin UV Ltd. UK, IST METZ GmbH Germany or Dr. Honle AG, Germany.

In order to gain a better distinction from the reactivity of tested photoinitiators and to investigate the kinetics of the reaction as a function of dose, the radically curable low-energy offset printing or letterpress ink described herein was cured in two dose of 100 mJ / cm2 (typical industrial dose) and 50 mJ / cm2 with a UV-LE lamp by varying the speed of the conveyor belt.

The process described herein is particularly suitable for producing a security feature on a substrate that is suitable as a substrate for a security document. According to a preferred embodiment, the security feature is used as background printing on the substrate for later printing or processing. This means that on top of the security feature printed by the process described herein, this is the image, pattern or graphic element that serves for authentication purposes, additional security features or non-security features are printed or applied in one or more additional printing or applying tours and the security feature printed by the process described herein and the additional security or non-security features overlap.

Typical substrate examples include without limitation fiber-based substrates, preferably cellulosic fiber-based substrates such as paper, paper-containing materials, polymer-based substrates, composite materials (for example substrates obtained by laminating layers of paper and polymer films ), metals or metallized materials, glasses, ceramics and combinations thereof. Typical examples of polymer-based substrates are substrates made of ethylene- or propylene-based homo- and copolymers such as polypropylene (PP) and polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). Typical examples of composite materials include without limitation multilayer structures (e.g. laminates) of at least one layer of paper and at least one polymer film, including polymers such as those described above, as well as substrates such as paper based on cellulosic fiber blends. and synthetic polymer fibers. In a preferred embodiment the security features are printed on a selected substrate of offset papers and fiat papers. Offset paper is made of wood pulp cellulose with properties that make the paper suitable for offset printing, including dimensional stability, resistance to curling, high surface resistance, a surface free of foreign particles and a high level of resistance to moisture penetration. Typically the basis weight of offset paper is 30 g / m2 to 250 g / m2, preferably 50 g / m2 to 150 g / m2.

Fiat paper (also known in the art as security paper) is made from lignin-free cotton pulp cellulose. Compared with offset papers, the additional properties of fiduciary papers include improved mechanical strength (especially resistance to tear and wear), resistance to fouling and treatment against degradation by micro-organisms (bacteria, viruses and fungi). The mechanical strength of fiat papers can be improved by the introduction into the paper pulp (cotton-based) of synthetic fibers, and the anti-stain performance can be improved by coating or printing an anti-soil polymeric layer before printing or apply the security features of the banknote. Generally, biocide treatment is combined with anti-soil treatment. Typically, fiat paper has a basis weight of 50 to 150 g / m2, preferably 80 to 120 g / m2.

Additionally, the use of fiat paper instead of offset paper adds an additional element of anti-counterfeiting protection, as fiat paper is manufactured on special papermaking machines that are only available to security paper manufacturers, and since the chain supply is protected such as to prevent fiduciary paper from being diverted to counterfeiters.

The term "security document" refers to a document that has such value as to be potentially liable for attempted counterfeiting or illegal reproduction and that is normally protected against forgery or fraud by one or more security features. Examples of security documents include without limitation documents of value and value of commercial property. Typical examples of valuable documents include without limitation bills, deeds, tickets, checks, vouchers, fiscal stamps and tax labels, agreements and the like, identity documents such as passports, identity cards, visas, bank cards, credit cards, transaction cards, access documents, security badges, entry tickets, transport tickets or titles, and the like.

The term "good commercial value" refers to packaging material, in particular for the pharmaceutical, cosmetic, electronic or food industry that may comprise one or more security features in order to ensure that the contents of the packaging are genuine, such as genuine drugs. Example of this packaging material includes without limitation labels such as authentication mark labels, tax flags, tamper evidence labels, and seals. The security document described herein may further comprise one or more additional layers or coatings either below or on top of the security feature described herein. In case the adhesion between the substrate and the security feature described herein is insufficient, for example due to substrate material, surface unevenness or surface inhomogeneity, an additional layer, coating or a primer between the substrate and the security feature could be applied as is known to those skilled in the art.

In order to further increase the level of security and resistance against forgery and illegal reproduction of security documents, the substrate may contain watermarks, security threads, fibers, plates, luminescent compounds, windows, foils, decals, coatings and combinations thereof.

The substrate described herein, in which the low energy radically curable offset printing or letterpress ink described herein is applied, may consist of an intrinsic part of a security document, or alternatively, the printing ink. Radically curable low energy offset or letterpress printing described herein is applied onto an auxiliary substrate such as for example a security thread, security strip, a foil, a decal or a label and consequently transferred to a security document. in a separate stage.

Also described herein are uses of one or more photoinitiators described herein to produce the radically curable low-energy offset printing or letterpress ink described herein, such radically curable low-energy offset printing ink. typeface being suitable for printing a security feature on a security document.

EXAMPLE

The present invention is now described in more detail with reference to non-limiting examples. The examples below provide more details for the preparation of low energy radically curable printing inks and the use of the photoinitiators according to the invention and comparative data.

Irradiation doses were determined using a Power Puck® II device. The irradiation source (medium pressure mercury lamp LE) was turned on. The Power Puck® II device was placed on the belt of the irradiation apparatus designed to receive the samples to be irradiated. The Power Puck® was irradiated with the irradiation source at different belt speed. The dose was obtained by adding the dose of the measured UVA, UVB and UVC from the Power Puck® II. The following values were obtained with a type J HUV lamp (Baldwin, Ozone-free lamp J7804045): 50 mJ / cm2 at 100 m / min, 100 mJ / cm2 at 50 m / min.

Influence of the photoinitiator on the whiteness of a printed and cured layer made of radically curable test varnishes

The radically curable whiteness test varnishes in Table 2 were prepared in order to evaluate the influence of the tested photoinitiators described in Table 1 on the whiteness (expressed in Berger degrees) of the printed test varnish layer after UV curing. .

Table 1: Photoinitiators

Table 2: Radically curable transparent whiteness test varnishes (whiteness evaluation)

Preparation of the radically curable whiteness test varnishes from Table 2

Radically curable clear whiteness test varnishes were prepared independently by mixing the ingredients described in Table 2 except the photoinitiator with an IKA T ULTRA TURRAX mixer until the temperature of the mixture reached 60-65 ° C.

The photoinitiators were added independently and the resulting mixtures were independently dispersed with a Speedmixer DAC 150 for three minutes, grinding in a Loher mill (3 x 50 laps with a weight of 7.5 kg) and dispersed again with a Speedmixer DAC 150 for three minutes.

Printing and Curing Method

The radically curable transparent whiteness test varnishes were independently printed on a substrate (fiat paper, Papierfabrik Louisenthal GmbH) in a Prüfbau at 800 N, to obtain a printing layer. The independently curable radically clear whiteness test varnishes were cured and dried with a Hg lamp (Aktiprint Mini 18.2) at a belt speed of 10 m / min to form cured printed test varnish layers. The exact amount of the printed and cured test varnish layers was calculated for each sample by weighing the substrate before and after printing. The weight of the printed and cured test varnish layers of all samples was 2 g / m2 ± 3%.

The substrates bearing the printed and cured test varnish layer were kept in the dark for five days and the whiteness of such samples independently and subsequently measured with a DC45 spectrophotometer: the whiteness value of the substrate (average value of three measurements) was subtracted from the whiteness value of the printed and cured test varnish layer (average value of three measurements). Larger negative values indicated stronger yellowing of the test and printed varnish layers. The whiteness of each sample is provided in Table 4.

Influence of the photoinitiator on the cure efficiency of a layer made of radically curable black fluorescent offset printing inks

The radically curable black fluorescent offset printing inks of Table 3 were prepared in order to evaluate the influence of the photoinitiators of Table 1 on the curing of such inks. The curing performance of each photoinitiator was evaluated by a back pressure test.

Table 3. Radically curable black fluorescent offset printing inks

Preparation of the radically curable black fluorescent offset printing inks from Table 3

Radically curable black fluorescent offset printing inks were prepared independently by mixing with the SpeedMixer ™ (DAC 150 SP CM31 from Hauschild Engineering) at room temperature the ingredients listed in Table 3, except the photoinitiators. The resulting pastes were independently ground in an SDY300 three-roll mill in three steps (a first pass at a pressure of 5 bar, a second and third pass at a pressure of 11 bar).

The photoinitiators were added independently to the pastes obtained as described herein and the inks thus obtained were mixed in a SpeedMixer ™ (DAC 150 SP CM31 from Hauschild Engineering) in a speed 2500 rpm for three minutes at room temperature, grinding in a Loher mill (3 x 50 turns with a weight of 7.5 kg), and mixing again with the SpeedMixer ™ for three minutes.

The viscosity of the radically curable black fluorescent offset printing inks from Table 2 was measured at 40 ° C and 1000 s-1 on a Haake Roto-Visco RV1 with a 2 cm 0.5 ° cone, linear speed increment 0- 1000 sec-1 in 30 seconds and are provided in Table 4.

Printing and Curing Method

Radically curable black fluorescent offset printing inks were independently printed as a pattern (4.5 cm x 23 cm) on a Guardian® substrate (Innovia) using a Prüfbau at a pressure of 1000 N (T = 22 ° C, relative humidity = 54%). The standards were divided into three parts and each sample was dried under two different doses of irradiation to evaluate the curing performance of the photoinitiator using a HUV type J lamp (Baldwin, Ozone-free Lamp J7804045). The belt speed of the curing dryer was selected according to the different doses tested as measured with a Power Puck® II UV radiometer from EIT, Inc., USA: 100 m / min for a dose of 50 mJ / cm2, 50 m / min for a dose of 100 mJ / cm2. The two doses were selected such as to discriminate the different reactivity of the photoinitiators tested and to investigate the kinetics of the reaction as a function of dose.

Back pressure cure test

For each sample, a drying test was carried out by forming an assembly consisting of a substrate sheet carrying the printed and cured ink layer and a fiduciary blank sheet placed on top of such a substrate carrying the layer. of printed and cured ink and presenting the assembly thus formed at a back pressure of 3.4 bar at 80 ° C with an ORMAG Intaglio Proof Press. The substrate bearing the cured printed ink layer and the fiat blank sheet were separated and the optical density of the fiat blank sheet was checked for ink transfer.

The measured optical density (Techkon SpectroDens Advanced, ISO 5-3 status E, Techkon GmbH Germany) from the back pressure test on the fiduciary blank sheet after contacting the uncured ink layer on the Guardian® substrate is defined as 0% cure. The measured optical density of the fiat blank sheet is defined as 100% cure (no relief). The measured optical density of each sample at the different irradiation doses is provided in Table 4.

Table 5 provides a summary of all the results.

Table 4: Whiteness Test Results and Cure Test Results

a) Margin of error: +/- 5%.

b) 100 mJ / cm2 corresponds to a typical industrial dose.

Table 5: summary of results

As shown in Tables 4 and 5, the photoinitiator P1 (used in E1) leads to good results not only in whiteness tests but also in back pressure tests even at very low irradiation doses (50 mJ / cm2). Considering that the inks comprising the photoinitiators P9 (used in C8) and P11 (used in C12), respectively, lead to good results in terms of curing performance at a low irradiation dose (at 50 mJ / cm2), an increase Dosing up to 100 mJ / cm2 did not result in an increase in curing performance to a level comparable to E1. Furthermore, the photoinitiator P9 (used in C8) exhibited very poor performance in terms of whiteness. All comparative examples P2-P8 and P12-P15 resulted in either negative yellowish performance (large negative whiteness test values) and / or poor cure performance.

Claims (10)

1. A radically curable low energy offset printing or letterpress ink having a viscosity in the range of 2.5 up to 25 Pa s at 40 ° C and 1000 s-1 for printing a security feature on a substrate or security document, radically curable low energy offset printing ink or letterpress printing ink, comprising: i) from 10% by weight to 80% by weight of radically curable (meth) acrylate compounds; ii) from 1% by weight to 20% by weight of one or more photoinitiators of formula (I):

where R ¹ , R ² are identical or different from each other and are selected from the group consisting of hydrogen, C1-C4 alkyls and Si (R ¹⁵ ) ³ ; preferably selected from the group consisting of hydrogen and C1-C4 alkyls, and more preferably hydrogen; R ³ , R ⁴ , R ⁵ , R ⁶ are identical to or different from each other and are selected from the group consisting of hydrogen and C1-C4 alkyls, preferably C1-C4 alkyls, and more preferably methyl; R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ are identical or different from each other and are selected from the group consisting of hydrogen, C1-C4 alkyls and halogens, preferably from the group consisting of hydrogen and C1-C4 alkyls, and more preferably hydrogen; Y R ¹⁵ is selected from the group consisting of C1-C4 alkyls, phenyl, C1-C4 hydroxyalkyls and C5-C8 cycloalkyls; iii) from 1% by weight to 60% by weight of one or more machine readable materials selected from the group consisting of luminescent materials, magnetic materials, IR absorbing materials and mixtures thereof; Y iv) from 0.5% by weight to 20% by weight of one or more fillers and / or diluents, Weight percentages are based on total weight of radically curable low energy offset printing or letterpress ink. 2. The low energy radically curable offset printing ink or letterpress printing ink according to claim 1, wherein at least one of one or more photoinitiators is of the formula (II):

The radically curable low energy offset printing or letterpress printing ink according to claims 1 or 2, wherein one or more fillers and / or diluents are selected from the group consisting of carbonates, silicas, talcs, clays and mixtures thereof. The low energy radically curable offset printing or letterpress ink according to any one of the preceding claims, wherein the radically curable (meth) acrylate compounds consist of one or more radically curable (meth) acrylate oligomers and one or more radically curable (meth) acrylate monomers. The radically curable low energy offset printing or letterpress ink according to any of the preceding claims, further comprising a) one or more colorants and / or b) inorganic pigments, organic pigments or mixtures thereof. The radically curable low energy offset printing or letterpress ink according to any of the preceding claims, further comprising one or more waxes selected from the group consisting of paraffin waxes, polyethylene waxes, fluorocarbon waxes, polytetrafluoroethylene waxes, carnauba waxes and mixtures thereof. 7. A process for printing a security feature on a substrate by an offset or letterpress printing process, comprising the steps of: a) applying the radically curable low energy offset printing or letterpress ink listed in any one of claims 1 to 6 by offset printing or letterpress printing to form a coating or layer, and b) curing the coating or layer with a UV lamp (280 to 400 nm) at a dose of at least 50 mJ / cm2, preferably at least 100 mJ / cm2. 8. A use of one or more photoinitiators listed in any one of claims 1 to 5 in an amount of from 1% by weight to 20% by weight to produce a radically curable low energy offset printing or letterpress ink. having a viscosity in the range of 2.5 up to 25 Pa s at 40 ° C and 1000 s-1, the radically curable low energy offset printing or letterpress ink being suitable for printing a security feature on a document Security, radically curable low energy offset printing or letterpress ink comprises: i) from 10% by weight to 80% by weight of radically curable (meth) acrylate compounds; ii) from 1% by weight to 60% by weight of one or more machine-readable materials selected from the group consisting of luminescent materials, magnetic materials, IR absorbing materials, and mixtures thereof; Y iii) from 0.5% by weight to 20% by weight of one or more fillers and / or diluents, Weight percentages are based on total weight of radically curable low energy offset printing or letterpress ink. A security feature, comprising a coating or a layer made of the radically curable low energy offset printing or letterpress ink according to any one of claims 1 to 6. 10. A security document, comprising one or more security features according to claim 9.